designed duct system can negatively impact an appliance's efficiency and life cycle, Figure 22. All systems require regularly scheduled maintenance. Gases The first step in dealing with gases is to minimize or eliminate the source when possible. Gases can come from building materials, carpet, aerosols, including hair sprays, perfumes, paint, varnishes, polyurethane, sealers, air fresheners, household cleaners, bleach, fuels, unvented combustion appliances, cook stoves and more. Gases can be managed with a properly designed ventilation system. A system can consist of spot exhaust ventilation when dealing directly with a source, such as the kitchen and bath exhaust. The best systems manage outside air intake with filtration and a control strategy. Remember, when exhausting air from a structure, replacement air will enter to balance the pressure differential. A good reliable source of managed intake air from outside is highly recommended. 24 National Oilheat Research Alliance When ventilation is not possible, there are other options, such as carbon filtration and/ or photo catalytic oxidation (PCO). PCO can reduce gases. Figures 24 on next page. The PCO units consist of a titanium dioxide-coated substrate and are illuminated with ultraviolet light. Such systems require adequate surface area to effectively reduce gases, and a small system with very little surface area placed into a residential duct system will have minimal effect. The Environmental Protection Agency (EPA) doesn’t recommend the use of ozone/activated oxygen in the residential occupied space for improving indoor air quality. Germs UVGI Ultra-Violet Germicidal Irradiation Germicidal lamps typically operate at a wavelength between 220 nanometers and 280 nanometers. The band is called UV-C. Some partially operate between 180 nanometers and 220 nanometers. The band is called UV-V. (Ozone producing band). The use of UVGI C band systems (Figure 23) can prevent microbial growth in drain pans and evaporator coils. Implementing a UVGI system with a dirty coil can allow dry airborne particulate to be distributed into the occupied Typical up-flow appliance with particulate capture in the return air duct Typical residential UVGI Products Figure 22 Figure 23
NORA Advanced Air Flow
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